1. Field of the Invention
The present invention relates to a process for placing a cement composition, and more particularly to a process for placing a cement composition having high strength.
2. Prior Art
In the prior art processes, the strength of cement mortar or concrete has been improved by the addition of a variety of cement admixtures of by mixing a reinforcing material, such as fibers or rods of glass or steel. However, the tensile and bending strengths cannot be appreciably improved by the former-mentioned admixture addition method, whereas the reinforced cement composition obtained by the latter-mentioned method is disadvantageously expensive with extra labor and costs required for mixing a reinforcing material although the properties, including the tensile and bending strengths, thereof is improved to some extent.
On the other hand, in order to prevent separation of concrete components and water-pollution problems which would arise when the concrete is placed in water, it has been proposed and adopted to add a viscosity increasing agent, examples of such viscosity increasing agent being polyvinyl alcohol, polyacrylamide, polyethylene oxide, sodium polyacrylate, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, sodium alginate and guar gum. However, the setting or hardening of the concrete is retarded by the addition of a viscosity increasing agent so that a relatively long time is required before the development of strength with another disadvantage that a large amount or number of bubbles is entrained by the viscosity increasing agent and is mixed in the concrete composition to lower the strength of the hardened concrete. For this reason, it has never been tried to improve the strength of a cement composition by the addition of such a viscosity increasing agent.